Outdoors the O2 Enviornment in London on Monday night, the hip-hop celebrity Pitbull tore right into a bowl of hen katsu curry. Just a few toes away, Pitbull fumbled with an iPhone charger. A lone Pitbull checked his watch, and a conga line of Pitbulls rode up an escalator. Two Pitbulls have been holding fingers. 4 extra break up a bottle of rosé.

The precise Pitbull — Armando Christian Pérez, a Miami native who steered a boisterous pressure of club-rap to the highest of the charts within the early 2010s — was backstage, getting ready for the primary of two performances on the 20,000-capacity area. Waves of younger followers have gotten within the behavior of impersonating the artist at every date of his “Get together After Darkish” tour, paying particular consideration to his most well-known, most hairless, characteristic.

“I’m fairly positive each celebration store in London is bought out of bald caps,” mentioned Jay McGillan, 19.

Mr. McGillan mentioned he had visited seven shops and struck out, so he improvised by drawing a portrait of Pitbull’s glowing pate straight onto the material of his white button-up shirt. He joined a line of followers streaming into the world, considered one of them carrying a T-shirt that learn: “Good ladies go to church … Dangerous ladies go to Pitbull.”

It’s growth occasions for the live performance uniform, a comparatively current phenomenon wherein followers coordinate on social media to put on sequins to see Taylor Swift and cowboy boots for Beyoncé. (Jimmy Buffett’s Parrotheads have been method forward of the curve.)

However Pitbull mania is an outlier by way of its outrageousness, its lack of apparent intercourse enchantment and its uniformity. To wander among the many Pitbulls looks like Halloween night time, if Halloween had just one costume choice and it was Pitbull.

On the sidewalk outdoors the stadium, followers punched up each other’s costumes with the power of a demented group challenge. Shannon Hilton, 25, used liquid eyeliner to attract a goatee on her pal Georgia Burdett. Each have been followers of Pitbull’s celebration anthems — “Fireball,” “Give Me Every part” — since they have been youngsters, they usually anticipated the present to be a nostalgia journey.

Ms. Burdett, 25, was within the means of Pitbull-ifying the black blazer and trousers she had worn to the workplace earlier that day. She checked out her new facial hair within the reflection of a pal’s telephone display. “Oh, I’m actually happy,” she mentioned.

A lot of the Pitbulls mentioned that they had gotten the thought to decorate up from TikTok or Instagram, the place movies of bald-capped followers have been circulating for the previous couple of years. However why had practically half of the group chosen to commit so totally to this explicit bit, on this explicit night time, that looking throughout the world felt like swimming in a sea of nude latex?

Ms. Hilton referred to as it a “mob mentality.” One other fan described it as “one huge inside joke.”

“As adults, you don’t actually have the possibility to be foolish and gown up as one thing ridiculous,” mentioned Uvie Emagbetere, 26, who had lower up a pair of stockings to kind her bald cap.

Her pal Sofia Sa, 27, had layered three wig caps for an ultrasmooth impact. “We now have grownup cash, and that is what this technology is selecting to spend it on,” she mentioned.

The person who launched a thousand bald caps by no means anticipated to have this many imitators. In an interview, Pitbull, 44, mentioned he had first observed a smattering of costumes when venues started to reopen from Covid-19 shutdowns. The frenzy reached one other degree throughout his European tour final 12 months.

“I used to be like, ‘Man, may as properly simply name them the baldies,’” he mentioned. “My grandmother all the time instructed me in Spanish that I must fly excessive, like an eagle.”

He mentioned he was touched that anybody needed to decorate up as him: “After we’re on the market having time, we’re hovering, and we’re flying excessive collectively.”

Pitbull emphasised that the bald cap phenomenon was not some sensible advertising ploy by his staff. (“We by no means tried to scheme!”) Although he has actually leaned into it this 12 months, posting montages of costumed followers on social media and shouting out the baldies onstage and in interviews. He now sells a “Mr. 305” package that comes with a bald cap and bow tie for $19.99.

The tour is heavy on hits from the 2010s, though he launched his twelfth studio album, “Trackhouse,” in 2023. He mentioned he was proud to draw followers of all ages. “My demographic is from the diaper to the diaper,” he mentioned.

He exploded onto the stage on Monday simply after 9:30 p.m., carrying a skintight leather-based bomber jacket and leaping up and right down to the beat of “Hey Child.” He thumped his chest, caught out his tongue and led the group in a call-and-response: “Who got here to celebration?” “We got here to celebration!”

The group of bald caps included college students, accountants, development staff and 10 members of a health group that always labored out whereas listening to Pitbull. Followers chucked seashore balls that seemed like globes towards the stage in reference to one of many artist’s nicknames, Mr. Worldwide.

Ross Ladbrook, 47, was smug when his buddies complained that their caps have been changing into uncomfortable. He had been bald ages earlier than Pitbull touched down in London, and his look was lastly au courant. “I really feel welcomed,” he mentioned.

Heidi Lees, 39, wore denims and a inexperienced T-shirt, her hair in a ponytail. “I’m too previous,” she mentioned of her lack of bald cap. “I didn’t understand it was a factor.” She had been stunned by the tireless parade of Pitbulls, however mentioned it had received her over with its absurdity: “People simply being people is enjoyable.”

Because the live performance wound down, the Pitbulls boarded the tube at North Greenwich station and peeled off their adhesive goatees. They shook out their sweaty hair. One Pitbull vomited right into a trash bag.

The spell had damaged. However after you have seen so many Pitbulls, it may be troublesome to see anything. Not removed from the stadium, I approached a lady carrying a canine with a wrinkled snout, questioning if she had introduced the pet as an particularly literal accent.

She didn’t appear conscious that there was a live performance occurring. “It’s an English bulldog,” she mentioned, tartly.